Prior to the present invention, fuel injector pumping systems for internal combustion engines have incorporated a delivery valve in the passages between a high pressure pump and the injector nozzles for the combustion chambers to serve as a one-way check valve to seal the pumping chamber from the injector lines while it is being charged with fuel and to control residual line pressure by providing volume unloading. Such valving often incorporates a snubber valve to control secondary injection of fuel through the nozzle and cavitation erosion of the high pressure system by attenuating reflected pressure waves. This is accomplished when the snubber valve closes at the termination of pumping by the pressure drop in the injection line. The retraction velocity and negative pressure wave reflected from the nozzle are reduced by the snubber valve restriction. With this partial pressure wave reduction, secondary waves reflected from the delivery valve to the nozzle are reduced to thereby reduce secondary injection of fuel into the associated combustion chamber. With secondary injection reduced, fuel injection and engine operating efficiency are enhanced to meet higher standards for even greater improvement in engine operating efficiency with reduced pollutants such as smoke and hydrocarbons.